Re: ferri sesquichlorati
The highest claim I read was from Paul Anderson (1917), who says that "....he gets all in 4-6 layers, but some give ten or twelve, one he knows gives twenty-five to thirty." (not exact quote). I think my most has been 8 but that usually is because I have failed at registration and keep trying to make it look better by one more layer and it never does so I rip it and throw it. I do 3-4, occasionally 5, most often 3.
BTW, Is there a maximum number of layers for gum, one book I have claim twelve or so, but have seen other claims of 20 .. ? Halvor